Meeting Abstract
Modern crocodylians employ immense forces during feeding. Many characters that enable crocodylians to generate and resist these forces are not found in their ancestors, and thus the evolution of crocodylians involved a substantial reorganization of the feeding apparatus. Once this suite of changes was in place, crocodyliforms radiated into forms with derived diets and craniodental modifications. To assess the biomechanical effects of changing configurations of muscles and cranial joints, we used CT data to create 3D models of extant and fossil suchians that demonstrate the evolution of the crocodylian skull, using osteological correlates to reconstruct muscles. Muscle forces were distributed with the computational package Boneload and used as input for finite element analysis and 3D lever analyses. We found that jaw muscles expanded and shifted attachments throughout suchian evolution: muscle orientations became more mediolateral as the skull flattened, the pterygoideus ventralis muscle began inserting on the lateral mandible, and the depressor mandibulae muscle expanded its attachment on the enlarged retroarticular process. Changes to cranial joints accompanied muscular changes: the pterygoid buttress expanded, the articular surfaces of the jaw joint changed, and the quadrate and palate sutured to the braincase. Our results showed that joint force orientation tracks with articular surface metrics. We found that as bite location moves caudally, working side joint force decreases in magnitude; it is likely that in feeding events such as shaking bites or death roll, the jaw joint is loaded in tension. This study depicts a feeding apparatus that defies traditional understanding. The combination of dual craniomandibular joints and jaw joints loaded in tension is unknown from the rest of tetrapods.
